It should be 12 volts. 6 volts is too small. I have a 12 volt battery on my 5hp generator. It's ok to use the jumper box.

OP, I see you are from NY. Do you have Verizon FIOS? If so, go to the backup box. There is a 12 volt battery in that box. You can use it for your tractor. You won't harm anything by taking the battery out of the box. That battery is for the phone line only in case you lose power.

I own a jumper pack and used it on my daily when I left a map light on all night, and also used it on my dad's old minivan with a big 4.2L in it when his battery died and I had to keep it going for a day so I could pick him up a new battery.

They're a must-have for not even auto enthusiasts, but anyone who drives a car every day. Do recommend for any petroleum-powered device with a 12v battery.